what are the benefits at having 2 graphics card and are they any dowsides /cheers
For most people, 2 graphics cards is overkill. Hardcore gamers are an example of someone who would be interested in this kind of setup.
If you are wanting to run the latest PC games at high resolutions on full settings then two graphics cards may be something worth looking into. If that is the case with you, just post back and we can help you pick the right setup.
The downsides are price of course, not only are two cards expensive, but also the costs of having other components that support diual cards (motherboard and power supply).
Two video cards will also allow you to run upto four monitors, provided the cards in question have two DVI ports.